Hi Sarah, On 9/16/25 15:35, Sarah Tarrant wrote:
Hi Martine,Thank you for your reply! Regarding:5) Would you like to participate in the RPC Pilot Test for editing in kramdown-rfc? If so, please let us know and provide a self-contained kramdown-rfc file. For more information about this experiment, see: https://www.rfc-editor.org/rpc/wiki/doku.php?id=pilot_test_kramdown_rfc.Since we edited the draft originally in kramdown-rfc, yes.Please send along the self-contained markdown file so we can get started!
Find attached. Best Martine
Sincerely, Sarah Tarrant RFC Production CenterOn Sep 16, 2025, at 5:34 AM, Martine Sophie Lenders <[email protected]> wrote:5) Would you like to participate in the RPC Pilot Test for editing in kramdown-rfc? If so, please let us know and provide a self-contained kramdown-rfc file. For more information about this experiment, see: https://www.rfc-editor.org/rpc/wiki/doku.php?id=pilot_test_kramdown_rfc.Since we edited the draft originally in kramdown-rfc, yes.
---
title: "ALPN ID Specification for CoAP over DTLS "
abbrev: "CoRE ALPN"
category: info
docname: draft-ietf-core-coap-dtls-alpn-05
submissiontype: IETF # also: "independent", "editorial", "IAB", or "IRTF"
number:
date:
consensus: true
v: 3
area: "Web and Internet Transport"
workgroup: "Constrained RESTful Environments"
keyword:
- CoRE
- CoAP
- SVCB
- DTLS
- ALPN
venue:
group: "Constrained RESTful Environments"
type: "Working Group"
mail: "[email protected]"
arch: "https://mailarchive.ietf.org/arch/browse/core/";
github: "core-wg/coap-dtls-alpn"
latest: "https://core-wg.github.io/coap-dtls-alpn/draft-ietf-core-coap-dtls-alpn.html";
author:
- fullname: Martine Sophie Lenders
org: TUD Dresden University of Technology
abbrev: TU Dresden
street: Helmholtzstr. 10
city: Dresden
code: D-01069
country: Germany
email: [email protected]
- name: Christian Amsüss
email: [email protected]
- fullname: Thomas C. Schmidt
organization: HAW Hamburg
street: Berliner Tor 7
city: Hamburg
code: D-20099
country: Germany
email: [email protected]
- name: Matthias Wählisch
org: TUD Dresden University of Technology & Barkhausen Institut
abbrev: TU Dresden & Barkhausen Institut
street: Helmholtzstr. 10
city: Dresden
code: D-01069
country: Germany
email: [email protected]
normative:
RFC6347: dtls12
RFC7252: coap
RFC7301: alpn
RFC9147: dtls13
RFC9460: svcb
informative:
RFC8323: coap-tcp
RFC8446: tls13
I-D.ietf-core-dns-over-coap: doc
RFC4944: 6lo
--- abstract
This document specifies an Application-Layer Protocol Negotiation (ALPN) ID for
transport-layer-secured Constrained Application Protocol (CoAP) services.
--- middle
# Introduction
Application-Layer Protocol Negotiation (ALPN) enables communicating parties to agree on an application-layer protocol during a Transport Layer Security (TLS) handshake using an ALPN ID {{-alpn}}.
This ALPN ID can be discovered for services as part of Service Bindings (SVCB) via the DNS, using SVCB resource records with the "alpn" Service Parameter Keys {{-svcb}}.
As an example, applications that use the Constrained Application Protocol (CoAP) {{-coap}} can obtain this information as part of the discovery of DNS over CoAP (DoC) servers (see {{Section 3.2 of -doc}}) that deploy TLS 1.3 {{-tls13}} as well as Datagram Transport Layer Security (DTLS) 1.2 or 1.3 {{-dtls12}} {{-dtls13}} to secure their messages.
This document specifies an ALPN ID for CoAP services that are secured by transport layer security using DTLS.
An ALPN ID for CoAP services secured by TLS has already been specified in {{-coap-tcp}}.
# Application-Layer Protocol Negotiation (ALPN) IDs
For CoAP over TLS, an ALPN ID was defined as "coap" in {{-coap-tcp}}.
As it is not advisable to re-use the same ALPN ID for a different transport layer, an ALPN for
CoAP over DTLS is registered in {{iana-coap-alpn}}.
ALPN ID values have variable length.
For CoAP over DTLS, a short value ("co") is allocated, as this can avoid fragmentation of Client Hello and Server Hello messages in constrained networks with link-layer fragmentation, such as 6LoWPAN {{-6lo}}.
To discover CoAP services that secure their messages with TLS or DTLS, the ALPN IDs "coap" and "co" can be used, respectively, in
the same manner as for any other service secured with transport layer security, as
described in {{-svcb}}.
The discovery of CoAP services that rely on other security mechanisms is out of the scope of this document.
# Security Considerations
Any security considerations on ALPN (see {{-alpn}}) and SVCB resource records (see {{-svcb}}) also apply to this document.
# IANA Considerations {#iana}
[^replace-xxxx]
[^replace-xxxx]: RFC Ed.: throughout this section, please replace
RFC-XXXX with the RFC number of this specification and remove this
note.
This document has the following actions for IANA.
## TLS ALPN for CoAP {#iana-coap-alpn}
The following entry has been added to the "TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs" registry, which is part of the "Transport Layer Security (TLS) Extensions" registry group.
* Protocol: CoAP (over DTLS)
* Identification sequence: 0x63 0x6f ("co")
* Reference: {{-coap}} and \[RFC-XXXX\]
Note that {{-coap}} does not define the use of the ALPN TLS extension during the DTLS connection handshake.
This document does not change this behavior, and thus does not establish any rules like those in {{Section 8.2 of -coap-tcp}}.
--- back
# Change Log
## Since [draft-ietf-core-coap-dtls-alpn-04]
- Address Deb Cooley's IESG ballot COMMENT
## Since [draft-ietf-core-coap-dtls-alpn-03]
- Make DTLS references normative
## Since [draft-ietf-core-coap-dtls-alpn-02]
- Address shepherd review
## Since [draft-ietf-core-coap-dtls-alpn-01]
- Address review by Esko Dijk
- Address review by Marco Tiloca
## Since [draft-ietf-core-coap-dtls-alpn-00]
- Fix ALPN ID for CoAP over TLS
- Change intended status to Informational
[draft-ietf-core-coap-dtls-alpn-04]: https://datatracker.ietf.org/doc/draft-ietf-core-coap-dtls-alpn/04/
[draft-ietf-core-coap-dtls-alpn-03]: https://datatracker.ietf.org/doc/draft-ietf-core-coap-dtls-alpn/03/
[draft-ietf-core-coap-dtls-alpn-02]: https://datatracker.ietf.org/doc/draft-ietf-core-coap-dtls-alpn/02/
[draft-ietf-core-coap-dtls-alpn-01]: https://datatracker.ietf.org/doc/draft-ietf-core-coap-dtls-alpn/01/
[draft-ietf-core-coap-dtls-alpn-00]: https://datatracker.ietf.org/doc/draft-ietf-core-coap-dtls-alpn/00/
# Acknowledgments
{:unnumbered}
We like to thank Rich Salz for the expert review on the "co" ALPN ID allocation.
We also like to thank Mohamed Boucadair and Ben Schwartz for their early review before WG adoption
of this draft and Esko Dijk, Thomas Fossati, and Marco Tiloca for their feedback and comments.
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